366 BOTANICAL GAZETTE [aay 
headed toward or away from the region of greater stimulation. They 
experience the conditions on.all sides before continuing in their new 
direction, just as do those sperms which attain their orientation by 
many small spiral swingings in different directions. Furthermore, 
their new direction does not always take them directly toward or 
away from the source of stimulation, and their subsequent orientation 
is then attained by successive changes of their course as described 
for other sperms. Their reactions thus seem to be of the same kind 
as those described for other sperms. Sperms which react in this 
manner form a small part of those observed, and the reactions of 
other sperms do not accord with the “local action theory.” It 
has been shown that some sperms collect in a region by strictly “ pho- 
botactic” responses. If we hold that the sperms described above 
react by “topotactic” movements, therefore, we must suppose that 
in both the positive and negative responses different sperms of the 
same species respond to the same stimulus by reactions of different 
natures. This is hard to believe. It seems, rather, that the sperms 
mentioned have their mechanisms of response called into play by 
the effect of the stimulant on the organism as a whole, and not by 
the action of the stimulant on local parts of the organism. 
The reactions of fern sperms thus seem to be of the same kind as 
those described for protozoa. 
Summary 
1. Entrance of sperms into archegonia was obtained in every 
combination of species tried. 
2, When the egg and sperm were of the same species, extrence 
into 97 archegonia, as shown by sections, resulted in 37 fusions; 
but when the egg and sperm were of different species, entrance into 
129 archegonia failed to give a single fusion. A similar result was 
obtained by replanting prothalli on soil after entrance had occurred. 
3- The results obtained, while not disproving the existence of 
fern hybrids, indicate that conclusions based on the structure of the 
sporophyte should not be accepted without additional experimental 
evidence, and show that not every combination of egg and sperm 
can result in a fusion. : 
4. Sperms of one species were observed within the archegonla 
of another species boring against the egg. The failure of such sperms 
